The superconductivity,structure and microstructure of BaYScCu oxides

We added small amount of Sc (0.05–0.35at.%) to BaYCu oxide and found that the superconductivity deteriorated drastically when the Sc content reached 0.325at.%. X-ray and electron diffraction showed that the orthorhombic perovskite structure changed to multi-phase structure with unidentified phases. The microstructures observed by TEM are of needle like morphology. Their phases are not yet identified.     

Superconductivity of LaMCuO system (MBa,Sr and Ca

Superconductivity of the compounds of LaMCuO system with K₂NiF₄ type structure has been studied. For the sintered compounds with MBa, Sr and Ca, the highest onset transition temperatures, T_ci, estimated from resistivity measurement are about 36.9K, 43.0K and 23.5K, respectively and the highest temperatures where the resistivity vanishes, T_cf, are about 27.8K, 34.0K and 15.5K, respectively. Almost complete Meissner effect has been confirmed by low frequency ac susceptibility measurement. Crystals of the compounds with MBa and Sr have been prepared. As the result of the preliminary experiment for a crystal with Ba, it is found that T_cf of the crystal is higher than any one of the sintered specimens with MBa, while the T_ci of the crystal is nearly the same as the highest one of the sintered specimens.     

Lattice dynamics and debye temperature of AlCu,AlSi and AlGe alloy systems

The lattice dynamics and specific heat at constant volume for AlCu alloy system is studied using our previous treatment based on the microscopic electronic theory. Considering the volume and electron density effect on the dynamical matrix of the pure constituent, we obtain the band and local mode frequencies at the temperature-dependent specific heat in the Al_1−x Cu_x solid solution. Then, using the data about the mean elastic wave and the specific heat extrapolated to the absolute zero temperature, the Debye temperature is presented for the Al_1−xCu_x, Al_1−xSi_x and Al_1−xGe_x alloy systems. The Debye temperature decreases as a function of the Cu atomic fraction x for Al_1−xCu_x alloy, and remarkably for Al_1−xSi_x and Al_1−xGe_x solid solutions.     

Zero resistance above 90K in superconducting oxides ErBaCuO and YbBaCuO

Superconductivity transition has been observed by electrical resistance and a.c. magnetic susceptibility measurements in ErBaCuO and YbBaCuO systems. The highest T_c(ϱ=0) is 90.3K for ErBaCuO and 91K for YbBaCuO.     

High Tc superconductivity of a TlBaCaCuO compound

A TlBaCaCuO_4.5+x compound has been investigated from the point of view of superconductivity. Depending on the heat treatment, one part of the samples exhibits superconductivity with an onset of 121 K and a zero resistivity of 106 K, while the other part of them shows only a sharp drop in resistivity at 130 K which hints at the existence of superconducting domains. This picture was confirmed by magnetic and ESR measurements giving possibility for estimation of the critical magnetic fields.     

Pd addition in high Tc YBaCuO oxide

A small amount of Pd addition increases T_c for the YBa₂Cu₃O_7−y oxide. The maximum offset, midpoint and onset temperatures of the YBa₂(Cu_0.999Pd_0.001)₃O_7−y oxide are 92.1, 95.0 and 105 K, respectively. Excess addition of Pd decreases T_c. The T_c change is consistent with the results of the lattice constants.     

Microscopic multicluster description of the 7Li7Be, 8Li8B and 9Li9C mirror nuclei

The ⁹Li and ⁹C mirror systems are investigated in a microscopic α+³H+n+n and α+³He+p+p multicluster framework using the stochastic variational method. Possibility of existence of neutron (proton) halo structure is studied. The quadrupole moment of ⁹C is predicted to be −5.04 e fm².     

Eu3+:Ln2O2S(Ln=Lu,Y,Gd,La)晶体的角重迭参数计算

本文使用角重迭模型(AOM),针对Eu3+:Ln2O2S(Ln=Lu,Y,Gd,La)晶体系列,在考虑硫和氧两种不同格位的情况下,对f电子的全部四个角重迭参数eσ、eπ、eδ和eφ进行了计算,得到了一些基本规律,即中心离子与配位体之间的共价性大小次序为Lu～Y>Gd>La,并且Ln-O键的共价性要强于Ln-S键.     

Molecular structure of cyclopropenylidene,HCCCH from the millimeter wave spectra of its isotopomers

The rotational spectra of the two ¹³C and of the D monoisotopic substitutions of cyclopropenylidene C₃H₂ have been measured up to 300 GHz. The determination of the rotational and centrifugal distortion constants of four isotopomers has led to a complete substitution structure. The values of the two CC bond lengths which define the three-membered ring have been improved by using Watson's “mass-dependence” (r_m) method.     

Zero resistance at 148.5K in fluorine implanted YBaCuO compound

Fluorine ions with an energy of 180keV at a dose of 1×10¹⁵ ions/cm² have been implanted into YBa₂Cu₃O_x. After annealed at 800°C, the resistance of the new Y-Ba-Cu-F-O compound drops to zero at 148.5K.     

Ion mixing of near surface layers in AuCu,CuMo systems irradiated by HPIB

New results on mixing in single layered metal structures exposed to nanosecond high power ion beams (HPIB) are presented. Au/Cu and Cu/Mo structures have been investigated using RBS, SIMS, AES and transmission electron microscopy. It is shown that HPIB-induced mixing was initiated at the substrate-deposited-layer interface in contrast to laser melting which starts at the surface. Cu₃Au superstructure phase, CuAu metastable state and an amorphous structure have been revealed. Cu/Mo structures which cannot produce equilibrium alloys and compounds and strongly differ in their thermophysical properties, can be mixed in the gaseous and liquid phases by three HPIB pulses with 0.95 J/cm² energy density.     

Electron diffraction and electron microscopic study of BaYCuO superconducting materials

Electron microscopy and electron diffraction have been applied to show that the orthorhombic phase in the compound Ba₂YCu₃O_7−δ is responsible for the high superconducting transition temperature. A positive correlation is found between the volume fration of the orthorhombic phase and the superconducting transition temperature. By means of an “in-situ” heating experiment it is found that the orthorhombic phase is formed on cooling from a high temperature tetragonal phase with disordered vacancies. It is suggested that the low temperature tetragonal phase that occurs in the same specimens as the orthorhombic phase also contains an ordered arrangement of vacancies different from that present in the orthorhombic phase. The order-disorder transition associated with the structural vacancies is shown to be reversible, provided there has been no oxygen loss.     

Electrical properties of LiBSe ternary system

Amorphous products were obtained in the LiBSe ternary system by quenching melts of Li₂Se, B and Se mixture prepared at 100°C in sealed silica tubes. The vitreous region was slightly lower selenium composition than that of the Li₂SeB₂Se₃ tie-line. The amorphous products were lithium ionic conductors and most of them showed contributions to their total conductivity. The amorphous product of composition Li₂₅B₃₆Se₃₉ has the least electronic contribution to its total conductivity of 6.0 × 10⁻⁶ S/cm at room temperature. A new crystalline compound and crystalline LiBH₄ were also obtained in LiBSe ternary. Both of them were lithium ionic conductors having conductivities of about 1 × 10⁻⁶ S/cm at room temperature.     

Superconductivity of TiZrNi alloys containing quasicrystals

Superconductivity of rapidly quenched ribbons Ti₅₃Zr₂₇Ni₂₀ at 1.94 K and the beginning of the transition to the superconductivity in ribbons Ti₄₅Zr₃₈Ni₁₇ below 1.5 K were found. X-rays diffractometry measurements showed that the icosahedral quasicrystal phase is dominant in all samples.